Walter Szulc Jr., in the kayak on the left, looks back at the dorsal fin of an approaching shark at Nauset Beach in Orleans, Mass., in Cape Cod, last weekend.

The previous week, a 3- to 5-metre great white shark was seen off Chatham in the first confirmed shark sighting of the season, according to a state researcher. Two more sightings were reported on July 2.

Sharks are drawn to the waters because they are filled with seals, which they like to eat.